1. Field of the Invention
This invention relates to flow effector design. More specifically, the invention is an active flow effector that can be coupled to a jet engine exhaust nozzle to affect the flow exiting therefrom.
2. Description of the Related Art
Reduction of jet engine noise in the vicinity of airports continues to be of paramount importance. Jet exhaust-nozzle chevron systems are a proven noise reduction technology, but much is yet to be learned about their parametric design space. Furthermore, a tradeoff between noise reduction at takeoff and thrust loss at cruise has slowed their incorporation into production engines. The presence of chevrons arranged about the periphery of a nozzle produces a scalloped (or serrated) trailing edge with the chevrons protruding into the flow, increasingly from root to tip, in the flow direction. Model-scale noise reduction and/or flow studies involving chevrons have generally been performed using static chevron technology where the geometry and resulting flow immersion is predetermined and invariant. These studies typically included some parametric investigation of chevron number geometry and degree of immersion. However, detailed parametric investigations using static chevrons are not feasible because of the high cost of fabricating and testing separate nozzle systems. Numerical studies are also limited for investigation of the parametric design space because of questionable fidelity in noise predictions. Furthermore, it is certain that parametric effects will vary from one engine to another and will be dependent upon operating conditions.
One means of simultaneously addressing some parametric design issues and the tradeoff of noise reduction and thrust penalty is the development of active chevrons. To date, active chevron development has focused on the attachment of shape memory alloy (SMA) bender elements to a chevron surface. However, this approach (i) suffers from space, mass and mechanical inefficiencies, (ii) requires auxiliary heating elements, (iii) produces undesirable deformation effects, and (iv) is subject to attachment problems.